在先前研究中，多能干細(xì)胞（iPS）可由成纖維細(xì)胞創(chuàng)造出來(lái)，成纖維細(xì)胞是一種特殊類型的皮膚細(xì)胞，能分化成其他類型的皮膚細(xì)胞。由于無(wú)法分辨這些成纖維細(xì)胞是否已*分化，先前實(shí)驗(yàn)中使用的細(xì)胞也許分化得比較少，因此更容易轉(zhuǎn)化為如同胚胎干細(xì)胞狀態(tài)的iPS細(xì)胞。
B細(xì)胞是一種能與特定抗原結(jié)合的免疫細(xì)胞，特定抗原是指諸如來(lái)自細(xì)菌、病毒或微生物的蛋白。與成纖維細(xì)胞不同的是，成熟B細(xì)胞的DNA有特定的一部分在zui終成熟階段會(huì)被剔除。論文的*作者，美國(guó)懷特黑德生物醫(yī)學(xué)研究所魯?shù)婪?middot;詹尼士實(shí)驗(yàn)室的博士后研究員雅克布·漢娜表示，那段DNA一旦被剔除，就無(wú)法再回來(lái)了。對(duì)基因組進(jìn)行檢查，就能給研究人員賦予一種方式來(lái)確定所產(chǎn)生的iPS細(xì)胞并非來(lái)自未成熟的細(xì)胞。
漢娜等人通過(guò)從成熟B細(xì)胞產(chǎn)生ips細(xì)胞開始實(shí)驗(yàn)。利用類似于以成纖維細(xì)胞制造iPS細(xì)胞的方法，研究人員使用反轉(zhuǎn)錄病毒將4個(gè)基因（Oct4、Sox2、c-Myc與Klf4）轉(zhuǎn)移至細(xì)胞的DNA中，成功地將成熟B細(xì)胞重組為iPS細(xì)胞。不過(guò)，研究人員還使用了另外一個(gè)因子CCATT/增強(qiáng)子結(jié)合蛋白（C/EBPα），來(lái)刺激成熟B細(xì)胞能被重組為如iPS般的細(xì)胞。
與先前成纖維細(xì)胞研究而來(lái)的iPS細(xì)胞一樣，來(lái)自成熟與非成熟B細(xì)胞的iPS細(xì)胞能用來(lái)制造老鼠。這些來(lái)自重組成熟B細(xì)胞的老鼠，同成熟B細(xì)胞一樣缺失了相同部分的DNA，這證明漢娜等人已成功地重組了已*分化的細(xì)胞。
除了證明重組的威力之外，該項(xiàng)研究也為諸如多發(fā)性硬化癥與Ⅰ型糖尿病等自身免疫疾病提供了功能強(qiáng)大的新的老鼠模型。例如，神經(jīng)細(xì)胞專有的成熟B細(xì)胞或T細(xì)胞——神經(jīng)膠質(zhì)細(xì)胞，可重組成iPS細(xì)胞，然后用于制造整個(gè)免疫系統(tǒng)主要只攻擊神經(jīng)膠質(zhì)細(xì)胞的老鼠，從而為多發(fā)性硬化癥的研究創(chuàng)造出一種老鼠模型。
詹尼士預(yù)言，研究人員zui終將能通過(guò)類似的方法用人類細(xì)胞來(lái)研究疾病。原則上，這使得研究人員可將復(fù)雜的人類遺傳疾病轉(zhuǎn)移到培養(yǎng)皿上來(lái)進(jìn)行研究，這將可能是分析疾病并確定療法的*步。
（Cell），Vol 133, 250-264, 18 April 2008，Jacob Hanna, Rudolf Jaenisch
Direct Reprogramming of Terminally Differentiated Mature B Lymphocytes to Pluripotency
Jacob Hanna,1 Styliani Markoulaki,1 Patrick Schorderet,1 Bryce W. Carey,1,2 Caroline Beard,1 Marius Wernig,1 Menno P. Creyghton,1 Eveline J. Steine,1 John P. Cassady,1,2 Ruth Foreman,1,2 Christopher J. Lengner,1 Jessica A. Dausman,1 and Rudolf Jaenisch1,2,Cell成熟B細(xì)胞可重組成干細(xì)胞狀態(tài)
1 The Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
2 Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
Summary
Pluripotent cells can be derived from fibroblasts by ectopic expression of defined transcription factors. A fundamental unresolved question is whether terminally differentiated cells can be reprogrammed to pluripotency. We utilized transgenic and inducible expression of four transcription factors (Oct4, Sox2, Klf4, and c-Myc) to reprogram mouse B lymphocytes. These factors were sufficient to convert nonterminally differentiated B cells to a pluripotent state. However, reprogramming of mature B cells required additional interruption with the transcriptional state maintaining B cell identity by either ectopic expression of the myeloid transcription factor CCAAT/enhancer-binding-protein-α (C/EBPα) or specific knockdown of the B cell transcription factor Pax5. Multiple iPS lines were clonally derived from both nonfully and fully differentiated B lymphocytes, which gave rise to adult chimeras with germline contribution, and to late-term embryos when injected into tetraploid blastocysts. Our study provides definite proof for the direct nuclear reprogramming of terminally differentiated adult cells to pluripotency.